The present invention is directed to a sleeve-shaped anchor member arranged to be fixed in a borehole by a permanently hardenable mass and the anchor member is provided with inwardly deformed areas at least over a portion of its axial length.
Anchor members securable by a permanently hardenable mass are used for many applications because of their advantages, such as the absence of expansion pressure, good durability on exposure to chemical and other external influences and because of a relatively simple installation procedure. Such known anchor members have not, however, been usable or have not afforded satisfactory service over long periods of time.
Until the present time there have been two different types of anchor members used. Where the anchor members are provided with external threads, as a rule, initially all of the hardenable mass is introduced into the borehole and then the anchor member is driven into the mass within the borehole with a rotational and/or percussion movement.
Where the anchor member is provided with internal threads so that a load attachment can be effected by a fastening element such as a screw, a threaded bolt, a threaded stud or the like, in most instances the anchor member is inserted into the borehole and then the hardenable mass is injected through the anchor members or directly into the annular space located between the anchor member and the borehole surface. Another possibility involves using a screen filled with the hardenable mass before insertion into the borehole. The mass is squeezed out of the screen or enclosure when the anchor member is inserted into the screen. Such a process is relatively cumbersome and results in problems, particularly with hardenable masses of low viscosity, that is, a very sticky mass. In both types of anchors there is a problem in obtaining an adequate positive lock or engagement of the anchor member in the hardenable mass. In addition, the inside thread in the anchor member can be clogged during the injection of the mass rendering the member unusable.
After the mass has partially or completely hardened, a fastening element with external threads is screwed into the internal thread of the anchor member. As a result, the anchor member held in place by the hardenable mass must provide a corresponding counter-torque so that the anchor member does not turn with the fastening element. To prevent turning of the anchor member, in a known embodiment the anchor member is secured in the hardenable mass by deformed areas on its peripheral surface and the deformed areas are also provided with outlet openings for the hardenable mass. Such deformed areas are sufficient for affording a positive lock in the axial direction of the anchor member with the hardenable mass. With regard to the prevention of rotation of the anchor member, such individual deformed areas have not been effective. If stress is applied to the anchor member very shortly after it is inserted into the mass and while the mass is not completely hardened, the required anchoring value can not be attained.
In the known anchor member the individual deformed areas are relatively deep so that an adequate contact between the anchor member and the hardenable mass in the region of the deformed areas is not always possible.